Circulating adrenaline is not involved in the circadian blood pressure profile

Background : Circadian changes in blood pressure are paralleled by analogous circadian changes in plasma catecholamines : blood pressure, plasma noradrenaline and adrenaline fall at night. Objective : To determine whether adrenaline is a prerequisite for the nocturnal fall in blood pressure, the circadian blood pressure profile was studied in adrenalectomized subjects, lacking circulating adrenaline. Subjects and methods : Ten adrenalectomized subjects and 10 healthy age-matched normotensive controls underwent 24-h non-invasive ambulatory blood pressure monitoring with the Oxford Medilog device. Measurements were taken every 15 min from 7.00 a.m. until 11.59 p.m and every 30 min from 12 midnight until 6.59 a.m. The nocturnal blood pressure fall was calculated for each subject. Results : Mean ± SD systolic blood pressure decreased at night by 13.2 ± 9.5 mmHg in the adrenalectomized and by 11.7 ± 7.3 mmHg (NS) in the control subjects. There was no significant difference between groups in the nocturnal diastolic blood pressure fall (14.4 ± 5.1 and 13.1 ± 5.2 mmHg, respectively). Systolic blood pressure decreased by >10 mmHg in five of the adrenalectomized and six of the control subjects. Diastolic blood pressure decreased by >10 mmHg in eight of the adrenalectomized and eight of the control subjects. Conclusion : The normal nocturnal fall in blood pressure in adrenalectomized subjects indicates that circulating adrenaline is not required for a normal circadian blood pressure rhythm.